Tissue-engineered growth of bone by marrow cell transplantation using porous calcium metaphosphate matrices

In this study we investigated not only osteoblastic cell proliferation and differentiation on the surface of calcium metaphosphate (CMP) matrices in v itro but also hone formation by ectopic implantation of these cell-matrix c onstructs in athymic mice in vivo. Interconnected porous CMP matrices with pores 200 mum in size were prepared to use as scaffolds for rat-marrow stro mal-cell attachment. Cell-matrix constructs were cultured in vitro, and cel l proliferation and ALPase activities were monitored for 56 days. in additi on to their being cultured in vitro, cell-matrix constructs were implanted into subcutaneous sites of athymic mice. In vitro these porous CMP matrices supported the proliferation of osteoblastic cells as well as their differe ntiation, as indicated by high ALPase activity. In vivo the transplanted ma rrow cells gave rise to bone tissues in the pores of the CMP matrices. A sm all amount of woven bone formation was detected first at 4 weeks; osteogene sis progressed vigorously with time, and thick lamellar bones that had been remodeled were observed at 12 weeks. These findings demonstrate the potent ial for using a porous CMP matrix as a biodegradable scaffold ex vivo along with attached marrow-derived mesenchymal cells for transplantation into a site for bone regeneration in vivo. (C) 2000 John Wiley & Sons, Inc.